Intense endurance exercise — such as running a marathon — may induce cardiac damage confined to the right ventricle, a small study showed. Highly trained endurance athletes had reductions in right ventricular function immediately after a race, although it mostly returned to normal about a week later, according to André La Gerche, MBBS, PhD, of the University of Melbourne in Australia, and colleagues. however, a handful of the athletes had signs of subclinical myocardial scarring on cardiac MRI, “suggesting that repetitive ultra-endurance exercise may lead to more extensive right ventricular change and possible myocardial fibrosis,” the researchers reported online in the European Heart Journal. Action Points  

• This study of 40 endurance athletes found evidence of right ventricular effects after an endurance event that largely resolved by six to 11 days later.
• Also, no concomitant left ventricular effects were observed.

There were no changes in left ventricular function, which “provides further circumstantial evidence for the emerging concept that the right ventricle may be more susceptible to exercise-induced injury [than the left],” they wrote.

The study included 40 athletes (mean age 37) who were participating in a marathon, an endurance triathlon, an alpine cycling race, or an ultra triathlon. all trained for more than 10 hours a week and had finished in the top quarter of a recent endurance race. none had cardiac symptoms or risk factors.

The researchers evaluated the athletes two to three weeks before the race, immediately after the race, and six to 11 days after the race.

Compared with baseline, right ventricular volumes increased, and all measures of right ventricular function worsened immediately post race. Left ventricular function was unaffected.

Levels of two biomarkers of myocardial injury — cardiac troponin I and B-type natriuretic peptide — significantly increased following the race (P≤0.003 for both). the changes were associated with reductions in right ventricular ejection fraction (P≤0.002 for both), but were unrelated to left ventricular ejection fraction.

Lower right ventricular ejection fraction was significantly associated with longer race duration and increasing peak oxygen uptake (P≤0.011 for both).

In the 39 athletes who underwent cardiac MRI, five had delayed gadolinium enhancement confined to the interventricular septum, indicative of subclinical myocardial fibrosis. these athletes had been competing in endurance sports longer and had lower right ventricular ejection fractions compared with those with normal MRI findings.

Because the study was not powered to assess clinical outcomes, the significance of the MRI findings requires further study, according to the authors.

The study “begs the hypothetical question whether repetitive longstanding bouts of arduous exercise result in the development of an acquired form of arrhythmogenic right ventricular cardiomyopathy,” Sanjay Sharma, MD, and Abbas Zaidi, MBBS, of St. George’s University of London, wrote in an accompanying editorial.

“The results provide food for thought and the data should be embraced to galvanize more detailed and longitudinal assessment of large groups of endurance athletes,” they wrote. “The potential for such projects is enormous considering the colossal increase in participation rates in endurance events such as the marathon.”

La Gerche is supported by a postgraduate scholarship from the National Health and Medical Research Council in Australia. the project was financed, in part, by a Cardiovascular Lipid Grant from Pfizer Australia.

The authors reported that they had no conflicts of interest.

The editorialists reported that they had no conflicts of interest.